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Difficulty: HardOSI Model Layers and Functions

A network analyst is investigating an automated host that fails to exchange data with a remote cloud API. Packet capture analysis confirms that physical media connections are operational, Ethernet frames are delivered without CRC errors, IP packets are routed across subnets without loss, and TCP three-way handshakes complete successfully. However, session logs reveal that communication terminates abruptly when the client and server attempt to negotiate character set encoding, data compression, and payload encryption standards. At which layer of the OSI reference model is this operational failure occurring?

  1. Presentation Layer (Layer 6)Answer
  2. B
    Session Layer (Layer 5)
  3. C
    Application Layer (Layer 7)
  4. D
    Transport Layer (Layer 4)

Answer

The operational failure is occurring at the Presentation Layer (Layer 6).
The correct answer identifies the Presentation Layer (Layer 6). This layer acts as the data translator for the network, handling tasks such as character encoding conversion (e.g., ASCII/EBCDIC), data compression, and encryption/decryption formatting so that differing systems can interpret payload syntax properly.

Step-by-Step Solution

1
Analyze lower-layer diagnostic status from the scenario.
Physical (Layer 1), Data Link (Layer 2), Network (Layer 3), and Transport (Layer 4) operations are confirmed working because TCP handshakes complete cleanly.
Eliminates lower layers (1-4) as potential failure points.
2
Identify the functional domain of the reported error.
The failure specifically involves character set encoding, data compression, and cryptographic syntax negotiation.
Isolates the specific network protocol responsibility being executed.
3
Map the functional domain to the correct OSI layer.
Layer 6 (Presentation Layer) handles translation, syntax presentation, encoding standards, compression, and encryption.
Matches the exact functional duties defined for Layer 6.

Key Concept

OSI Layer 6 (Presentation Layer) functions including data translation, character encoding, syntax presentation, compression, and encryption.
Estimated Time:2m 0s
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Topics

OSI Model Layers and Functions

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